AN EXAMPLE OF EPISODIC MIXING EVENT CAUSED BY STORM IN THE NORTHERN PART OF LAKE LADOGA

One of the aims of joint Finnish-Russian studies of Lake Ladoga (north-western Russia) was to estimate the temporal and spatial variability of different limnological parameters. Hydrochemical survey conducted in the vicinity of town Sortavala with daily sampling interval revealed a strong mixing event on 8th of August, 1995. Resuspension of bottom polluted sediments was clearly seen in the vertical profiles of O2 and Fe. The water temperature in epilimnion was decreased from 18 C to 13 C. Meteorological observations showed the intensification of the north-westerly winds during the same period of time. A two-dimensional circulation model was applied to simulate the currents under the unsteady wind conditions. Simulation results indicated the intensification of the advection flow from the open part of the lake that possibly caused the observed mixing episode.